At the same time, the markets contracted a case of Internet fever. This year many shares of fast-growing technology companies doubled, and price-to-earnings ratios topped 30. "The Chinese ETFs that have done well are the ones focused on the Internet and consumers," says Dennis Hudachek, an ETF analyst for IndexUniverse.com.

Despite the variety of the ETFs, no one choice may suit the needs of passive investors who seek to cover an entire market. Most China ETFs focus on narrow niches or subgroups such as stocks that trade outside the mainland. Hudachek recommends that passive investors start with SPDR S&P China, which is among the broadest choices. The ETF holds 230 stocks, with 27% in financial services, 17% in technology, and the rest scattered in sectors such as energy and materials. The portfolio includes stocks that trade in China and abroad.

The SPDR fund does not include A shares, stocks that are incorporated on the mainland and only trade there. In the past, foreign investors could not own A shares. But now foreigners can get access through a new ETF, db X-trackers Harvest CSI 300 China A-Shares (ASHR). By combining the new fund with the older SPDR choice, investors can cover all the bases, says Hudachek.

The biggest and oldest ETF is iShares China Large-Cap, with $5.7 billion in assets. Holding only 25 stocks, the fund has 52% of assets in financials and 7% in technology. Because the portfolio only includes stocks that are traded in Hong Kong, the ETF cannot own some of the biggest Internet names. Among the stocks that are off-limits is Baidu (BIDU), a search engine giant that trades in New York and has a market capitalization of $50 billion.